This color image from NASA's Curiosity rover shows an area excavated by the blast of the Mars Science Laboratory's descent stage rocket engines. This is part of a larger, high-resolution color mosaic made from images obtained by Curiosity's Mast Camera

With the loose debris blasted away by the rockets, details of the underlying materials are clearly seen. Of particular note is a well-defined, topmost layer that contains fragments of rock embedded in a matix of finer material. Shown in the inset in the figure are pebbles up to 1.25 inches (about 3 centimeters) across (upper two arrows) and a larger clast 4 inches (11.5 centimeters) long protruding up by about 2 inches (10 centimeters) from the layer in which it is embedded. Clast-rich sedimentary layers can form in a number of ways. Their mechanisms of formation can be distinguished by the size, shape, surface textures and positioning with respect to each other of the fragments in the layers.

The images in this mosaic were acquired by the 34-millimeter Mastcam over about an hour of time on Aug. 8, 2012 PDT (Aug. 9, 2012 EDT)

NASA's Curiosity rover found evidence for an ancient, flowing stream on Mars at a few sites, including the rock outcrop pictured here, which the science team has named "Hottah" after Hottah Lake in Canada's Northwest Territories. It may look like a broken sidewalk, but this geological feature on Mars is actually exposed bedrock made up of smaller fragments cemented together, or what geologists call a sedimentary conglomerate. Scientists theorize that the bedrock was disrupted in the past, giving it the titled angle, most likely via impacts from meteorites.

The key evidence for the ancient stream comes from the size and rounded shape of the gravel in and around the bedrock. Hottah has pieces of gravel embedded in it, called clasts, up to a couple inches (few centimeters) in size and located within a matrix of sand-sized material. Some of the clasts are round in shape, leading the science team to conclude they were transported by a vigorous flow of water. The grains are too large to have been moved by wind.

Broken surfaces of the outcrop have rounded, gravel clasts, such as the one circled in white, which is about 1.2 inches (3 centimeters) across. Erosion of the outcrop results in gravel clasts that protrude from the outcrop and ultimately fall onto the ground, creating the gravel pile at left.

This image mosaic was taken by Curiosity's 100-millimeter Mastcam telephoto lens on its 39th Martian day, or sol, of the mission (Sept. 14, 2012 PDT/Sept. 15 GMT).

Small spherical objects fill the field in this mosaic combining four images from the Microscopic Imager on NASA's Mars Exploration Rover Opportunity. Image credit: NASA/JPL-Caltech/Cornell Univ./ USGS/Modesto Junior College

NASA's long-lived rover Opportunity has returned an image of the Martian surface that is puzzling researchers.

Spherical objects concentrated at an outcrop Opportunity reached last week differ in several ways from iron-rich spherules nicknamed "blueberries" the rover found at its landing site in early 2004 and at many other locations to date.

Opportunity is investigating an outcrop called Kirkwood in the Cape York segment of the western rim of Endeavour Crater. The spheres measure as much as one-eighth of an inch (3 millimeters) in diameter. The analysis is still preliminary, but it indicates that these spheres do not have the high iron content of Martian blueberries.

"This is one of the most extraordinary pictures from the whole mission," said Opportunity's principal investigator, Steve Squyres of Cornell University in Ithaca, N.Y. "Kirkwood is chock full of a dense accumulation of these small spherical objects. Of course, we immediately thought of the blueberries, but this is something different. We never have seen such a dense accumulation of spherules in a rock outcrop on Mars."

The Martian blueberries found elsewhere by Opportunity are concretions formed by action of mineral-laden water inside rocks, evidence of a wet environment on early Mars. Concretions result when minerals precipitate out of water to become hard masses inside sedimentary rocks. Many of the Kirkwood spheres are broken and eroded by the wind. Where wind has partially etched them away, a concentric structure is evident.

Opportunity used the microscopic imager on its arm to look closely at Kirkwood. Researchers checked the spheres' composition by using an instrument called the Alpha Particle X-Ray Spectrometer on Opportunity's arm.

"They seem to be crunchy on the outside, and softer in the middle," Squyres said. "They are different in concentration. They are different in structure. They are different in composition. They are different in distribution. So, we have a wonderful geological puzzle in front of us. We have multiple working hypotheses, and we have no favorite hypothesis at this time. It's going to take a while to work this out, so the thing to do now is keep an open mind and let the rocks do the talking."

Just past Kirkwood lies another science target area for Opportunity. The location is an extensive pale-toned outcrop in an area of Cape York where observations from orbit have detected signs of clay minerals. That may be the rover's next study site after Kirkwood. Four years ago, Opportunity departed Victoria Crater, which it had investigated for two years, to reach different types of geological evidence at the rim of the much larger Endeavour Crater.

The rover's energy levels are favorable for the investigations. Spring equinox comes this month to Mars' southern hemisphere, so the amount of sunshine for solar power will continue increasing for months.

"The rover is in very good health considering its 8-1/2 years of hard work on the surface of Mars," said Mars Exploration Rover Project Manager John Callas of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Energy production levels are comparable to what they were a full Martian year ago, and we are looking forward to productive spring and summer seasons of exploration."

NASA launched the Mars rovers Spirit and Opportunity in the summer of 2003, and both completed their three-month prime missions in April 2004. They continued bonus, extended missions for years. Spirit finished communicating with Earth in March 2010. The rovers have made important discoveries about wet environments on ancient Mars that may have been favorable for supporting microbial life.

Curiosity on Mars sits on rocks similar to those found in marshes in Mexico

Millions of years ago fire and water forged the gypsum rocks locked in at Cuatro Ciénegas, a Mexican valley similar to the Martian crater where NASA's Rover Curiosity roams. A team of researchers have now analysed the bacterial communities that have survived in these inhospitable springs since the beginning of life on Earth. "Cuatro Ciénegas is extraordinarily similar to Mars. As well as the Gale crater where Curiosity is currently located on its exploration of the red planet, this landscape is the home to gypsum formed by fire beneath the seabed," as explained by Valeria Souza, evolutionary ecologist at the National Autonomous University of Mexico (UNAM).

The researcher states that sulphur components from magma and minerals from the sea (carbonates and molecules with magnesium) are required to form gypsum. In the case of the Cuatro Ciénegas Basin, the magma under the seabed was very active. In fact, it allowed for the continent displacement during the Jurassic Period: "Here was where the supercontinent Pangea opened up some 200 million years ago, pushing the hemisphere north from the equator where it is now."

In the case of Mars, the scientists have not been able to confirm tectonic movement in its crust at any point, but they believe that a large meteorite crashed into its primitive sea. The fact that probing has detected gypsum in the Gale crater indicates that mineral-rich water was present and that sulphur was able to form due to the impact of the meteorite causing the crater.

It is no easy task to find a place on Earth similar to this Martian environment, except in Cuatro Ciénegas. For this reason astrobiologists toil in their work to understand how its bacterial communities work. "This oasis in the middle of the Chihuahua desert is a time machine for organisms that, together as a community, have transformed our blue planet yet have survived all extinctions. How they have managed to do this can be revealed by their genes," says Souza.

The team have analysed the 'metagenomes', the genome of the different bacterial communities that proliferate in these marshes by adapting parallel strategies to overcome survival challenges in a place with so little nutrients.

Green, red and blue springs

The results published in the journal Astrobiology reflect the existence of two communities in different pits for example. One is 'green' and is formed by cyanobacteria and proteobacteria that have adapted to the lack of nitrogen. Another is 'red' and is made of Pseudomonas and other micro-organisms that live without hardly any phosphorus. There are also blue springs which are generally deeper and lacking in nutrients.

"Understanding the usage and exploitation strategies of phosphorus is necessary in understanding what could happen in extreme scenarios like on other planets where there is a possibly serious limitation to this and other nutrients," explains Luis David Alcaraz, Mexican researcher participating in the study from the Higher Public Health Research centre of Valencia, Spain.

This project has enjoyed the support of Mexico's Carlos Slim Foundation and the Technological Innovation Research Project Support Programme of UNAM. It has also received the support of the National Science Foundation (NSF) of the USA and NASA, which has been studying Cuatro Ciénegas for more than a decade.

The Cuatrociénegas Flora and Fauna Protection Area is a protected area but the scientists and conservation groups are worried that its water is being over exhausted. "The bacterial communities have survived all types of cataclysms here such as the extinction of the dinosaurs or the majority of marine creatures. But, the only thing they are not adapted for is the lack of water," warns Souza.

The first drill sample ever collected on Mars will come from a rockbed shot through with unexpected veins of what appears to be the mineral gypsum.

Delighted members of the Curiosity science team announced Tuesday that the rover was now in a virtual "candy store" of scientific targets—the lowest point of Gale crater, called Yellowknife Bay, is filled with many different materials that could have been created only in the presence of water. (Related: "Mars Has 'Oceans' of Water Inside?")

Project scientist John Grotzinger, of the California Institute of Technology in Pasadena, said during a press conference that the drill area has turned out "to be jackpot unit. Every place we drive exposes fractures and vein fills."

Mission scientists initially decided to visit the depression, a third of a mile from Curiosity's landing site, on a brief detour before heading to the large mountain at the middle of Gale Crater. But because of the richness of their recent finds, Grotzinger said it may be some months before they begin their trek to Mount Sharp.

The drilling, expected to start this month, will dig five holes about two inches (five centimeters) into bedrock the size of a throw rug and then feed the powder created to the rover's two chemistry labs for analysis.

The drill is the most complex device on the rover and is the last instrument to be used. Project Manager Richard Cook, of NASA's Jet Propulsion Laboratory, said that operating it posed the biggest mechanical challenge since Curiosity's high-drama landing. (Watch video of Curiosity's "Seven Minutes of Terror.")

A Watery Past?

That now-desiccated Mars once had a significant amount of surface water is now generally accepted, but every new discovery of when and where water was present is considered highly significant. The presence of surface water in its many possible forms—as a running stream, as a still lake, as ground water soaked into the Martian soil—all add to an increased possibility that the planet was once habitable. (Watch a video about searching for life on Mars.)

And each piece of evidence supporting the presence of water brings the Curiosity mission closer to its formal goal—which is to determine whether Mars was once capable of supporting life.

Curiosity scientists have already concluded that a briskly moving river or stream once flowed near the Gale landing site.

The discovery of the mineral-filled veins within Yellowknife Bay rock fractures adds to the picture because those minerals can be deposited only in watery, underground conditions.

The Curiosity team has also examined Yellowknife Bay for sedimentary rocks with the rover's Mars Hand Lens Imager (MAHLI). Scientists have found sandstone with grains up to about the size of a peppercorn, including one shaped like a flower bud that appears to gleam. Other nearby rocks are siltstone, with grains finer than powdered sugar. These are quite different from the pebbles and conglomerate rocks found in the landing area, but all these rocks are evidence of a watery past. (Related: "A 2020 Rover Return to Mars?")

One of the primary reasons Curiosity scientists selected Gale crater as a landing site was because satellite images indicated that water-formed minerals were present near the base of Mount Sharp. Grotzinger said that the minerals' presence so close to the landing site, and some five miles from the mountain, is both a surprise and an opportunity.

The current site in Yellowknife Bay is so promising, Grotzinger said, that he would have been "thrilled" to find similar formations at the mission's prime destination at the base of Mount Sharp. Now the mission can look forward to the surprises to come at the mountain base while already having struck gold.

This is a conception view of the Western hemisphere of Mars with oceans and clouds. Olympus Mons is visible on the horizon beyond the Tharsis Montes volcanoes and the Valles Marineris canyons near the center.

The Curiosity rover hit the science “jackpot” and has discovered widespread further evidence of multiple episodes of liquid water flowing over ancient Mars billions of years ago when the planet was warmer and wetter, scientists announced. The watery evidence comes in the form of water bearing mineral veins, cross-bedded layering, nodules and spherical sedimentary concretions.